This specification relates to image labeling.
The Internet provides access to a wide variety of resources, for example, video or audio files, web pages for particular subjects, book articles, and news articles. Users communicate across the internet using various forms of communication, such as electronic mail, discussion groups, blogs, and personal web pages.
A search system can identify resources in response to a text query that includes one or more search terms or phrases. The search system ranks the resources based on their relevance to the query and on measures of quality of the resources and provides search results that link to the identified resources. The search results are typically ordered for viewing according to the rank.
To search image resources, a search system can determine the relevance of an image to a query based on labels associated with an image. A label typically describes a category or topic for an image, or content depicted in an image, and is readable by a human or a computer (or both). The search system can rank images based on the relevance of the query to the various labels associated with the images, and produce image search results based on the rankings.
Labels associated with a particular image may be manually associated with the image by a user or automatically associated using computer vision techniques. In some cases, labels are created automatically for an image by a computer using computer vision techniques. However, manually associating labels with an image is time-consuming and rarely done in a consistent manner across different users. In addition, computer vision techniques are limited to what a computer can detect in an image, which may limit the accuracy of the labels.